Zlatina Asenova Genisheva

Early leaf removal impact on volatile composition of Tempranillo wines

BACKGROUND Early defoliation is a very innovative technique in viticulture used for yield management. The effects of early leaf removal performed manually and mechanically at two different phenological stages, pre-bloom and fruit set, on the volatile composition of Tempranillo (Vitis vinifera L.) wines were studied. Volatiles were identified and quantified by gas chromatography. RESULTS Early leaf removal only modified the total concentrations of C₆ compounds and acetates, whereas total alcohols, esters, volatile acids and terpenes remained generally unaffected. Early defoliation induced a significant reduction in C₆ compounds and increased the concentrations of acetates in Tempranillo wines. An effect of timing (pre-bloom vs fruit set) alone was observed for all acetates analysed. Regarding the method of defoliation (manual vs mechanical), significant differences in some ethyl ester (ethyl-2-methylbutyrate and ethyl octanoate) and volatile acid concentrations were observed among treatments. Ethyl octanoate, 2-phenylethyl acetate, 3-methylbutyl acetate and hexanoic acid, with OAV (odour activity value) > 1 and mainly fruity and floral odour descriptors, showed higher levels after early defoliation treatments compared with non-defoliated vines. Principal component analysis illustrated the difference in wines from defoliated and non-defoliated treatments based on their volatile composition. CONCLUSION It can be concluded that early leaf removal significantly modified the wine aroma compounds, increasing or decreasing several of these compounds.

Malolactic fermentation of wines with immobilised lactic acid bacteria - influence of concentration, type of support material and storage conditions.

Corn cobs, grape skins and grape stems were evaluated as support materials for immobilization of the lactic acid bacteria Oenococcus oeni. The support materials with immobilized cells were further used in malolactic fermentation (MLF) of white wine. Viability of using the immobilized supports was evaluated in consecutive batch fermentations under different conditions of temperature, ethanol and SO(2). Additionally, the possibility of storage and operational stability of the immobilized supports was also studied. All the three supports presented large potential for immobilization of O. oeni cells. The consecutive batches of MLF were successfully conducted for a total period of around 5 months with the possibility of storage of the biocatalyst for 30 d in wine at 25°C.

Determination of odorants in varietal wines from international grape cultivars (Vitis vinifera) grown in NW Spain

This work was carried out to investigate the odorants found in ten varietal wines from different international grape cultivars (Merlot, Cabernet Sauvignon, Pinot noir, Tempranillo, Sauvignon blanc, Riesling, Chardonnay, Pinot gris, Pinot blanc and Gewurztraminer) grown in northwest Spain. Monoterpenes, alcohols, fatty acids, ethyl esters, acetates and volatile phenols were determined by gas chromatographymass spectrometry (GC-MS). The results showed that Gewurztraminer white wines had the highest concentration of volatile compounds (35.7 mg/L). Monoterpenes, linalool, terpineol, citronellol and nerol were detected only in Riesling and Gewurztraminer white wines. In the red wines, Cabernet Sauvignon followed by Merlot wines showed the highest concentration of total volatile composition (55.60 mg/L and 50.90 mg/L respectively), characterised by a higher concentration of alcohols. Based on the individual odour threshold, white Gewurztraminer and red Pinot noir wines showed the highest total OAV value. ANOVA has shown significant differences among wines. Principal component analysis performed a grouping of the monovarietal wines – Sauvignon blanc-Pinot blanc-Riesling and Pinot gris gris-Gewurztraminer in the white wines, and Cabernet Sauvignon-Tempranillo in the red wines.

Electric field-based technologies for valorization of bioresources

This review provides an overview of recent research on electrotechnologies applied to the valorization of bioresources. Following a comprehensive summary of the current status of the application of well-known electric-based processing technologies, such as pulsed electric fields (PEF) and high voltage electrical discharges (HVED), the application of moderate electric fields (MEF) as an extraction or valorization technology will be considered in detail. MEF, known by its improved energy efficiency and claimed electroporation effects (allowing enhanced extraction yields), may also originate high heating rates - ohmic heating (OH) effect - allowing thermal stabilization of waste stream for other added-value applications. MEF is a simple technology that mostly makes use of green solvents (mainly water) and that can be used on functionalization of compounds of biological origin broadening their application range. The substantial increase of MEF-based plants installed in industries worldwide suggests its straightforward application for waste recovery.

Effect of Vertical Shoot-Positioned, Scott-Henry, Geneva Double-Curtain, Arch-Cane, and Parral Training Systems on the Volatile Composition of Albariño Wines

Viticultural practices influence both grape and wine quality. The influence of training systems on volatile composition was investigated for Albariño wine from Rías Baixas AOC in Northwest Spain. The odoriferous contribution of the compounds to the wine aroma was also studied. Volatile compounds belonging to ten groups (alcohols, C6-compounds, ethyl esters, acetates, terpenols, C13-norisoprenoids, volatile phenols, volatile fatty acids, lactones and carbonyl compounds) were determined in Albariño wines from different training systems, Vertical Shoot-Positioned (VSP), Scott-Henry (SH), Geneva Double-Curtain (GDC), Arch-Cane (AC), and Parral (P) during 2010 and 2011 vintages. Wines from GDC showed the highest total volatile composition with the highest concentrations of alcohols, ethyl esters, fatty acids, and lactones families. However, the highest levels of terpenes and C13-norisoprenoids were quantified in the SH system. A fruitier aroma was observed in Albariño wines from GDC when odor activity values were calculated.

New PLS analysis approach to wine volatile compounds characterization by near infrared spectroscopy (NIR)

This work aims to explore the potential of near infrared (NIR) spectroscopy to quantify volatile compounds in Vinho Verde wines, commonly determined by gas chromatography. For this purpose, 105 Vinho Verde wine samples were analyzed using Fourier transform near infrared (FT-NIR) transmission spectroscopy in the range of 5435 cm-1 to 6357 cm-1. Boxplot and principal components analysis (PCA) were performed for clusters identification and outliers removal. A partial least square (PLS) regression was then applied to develop the calibration models, by a new iterative approach. The predictive ability of the models was confirmed by an external validation procedure with an independent sample set. The obtained results could be considered as quite good with coefficients of determination (R2) varying from 0.94 to 0.97. The current methodology, using NIR spectroscopy and chemometrics, can be seen as a promising rapid tool to determine volatile compounds in Vinho Verde wines.